Oil and motor cooling in a refrigeration system



Oct. 29, 1968 D. K. RICHARDSON ET AL 3,407,623

OIL AND MOTOR COOLING 1N A REFRIGERATION SYSTEM Filed March 21, 1967INVENTORS= DOUGLAS K. RICHARDSON,

JOHN G. JOHNSON, gym? J,?.L

' ATTORNEY United States Patent O 3,407,623 OIL AND MOTOR COOLING IN AREFRIGERATION SYSTEM Douglas K. Richardson, Staunton, and John G.

Johnson, Waynesboro, Va., assignors to Westinghouse ElectricCorporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar.21, 1967, Ser. No. 624,746 2 Claims. (Cl. 62-197) ABSTRACT OF THEDISCLOSURE In a refrigeration system having a refrigerantcompressor-motor unit, lubricating oil from the unit is circulatedthrough tubes within an oil cooler compartment in the lower portion ofthe motor casing. Refrigerant from the condenser of the system issupplied through a thermostatic expansion valve into the oil coolercompartment around the tubes therein, then into the motor comparte mentaround the motor therein, and then through a suction gas tube to thecompressor. The diaphragm chamber of the expansion valve is connected toa thermal bulb in contact with the suction gas tube. The expansion valve`has a bleed port sized to supply sufficient refrigerant to properlycool the oil regardless of the modulation of the expansion valve causedby varying motor loads.

Background of the invention The iield of the invention is refrigerationsystems having refrigerant compressor-electric motor units, thelubricating oil of which has to be cooled. It is usual to cool the oiland a motor with two refrigerant circuits. This invention cools both inone circuit, with the oil cooler located upstream with respect torefrigerant flow of the motor. A single expansion valve responsive tosuperheat in the gas leaving the motor compartment controls therefrigerant ow. A feature of this invention is that the expansion valveis provided with a bleed port sized to supply sufficient refrigerant tothe oil cooler compartment to properly cool the oil regardless of themodulation of the expansion valve.

Summary of the invention The electric motor of a refrigerantcompressor-electric motor unit has a casing having an upper motorcompartment and a lower oil cooler compartment. The bottom wall of thecasing forms the bottom of the oil cooler compartment, and has arefrigerant inlet opening therein. The casing has an intermediate wallforming the bottom of the motor compartment and the top of the oilcooler compartment, and has an opening therein for admitting refrigerantleaving the oil cooler compartment into the motor compartment. Thecasing has a refrigerant outlet in its top wall connected through asuction gas tube to the suction gas inlet of the compressor. Thecondenser of the system including the compressor is connected through athermostatic expansion valve to the refrigerant inlet opening with thediaphragm chamber of the expansion valve connected to a thermal bulb incontact with the suction gas tube at the refrigerant outlet of the motorcasing. The expansion valve has a bleed port sized to supply sufficientrefrigerant to the oil cooler to properly cool the oil regardless of themodulation of the expansion valve caused by varying motor cooling loads.

Brief description of the drawings FIG. 1 is a diagrammatic View of arefrigeration system embodying this invention, and

FIG. 2 is an enlarged side view, partially in section, of the commoncasing of the oil cooler and electric motor of Fice FIG. l, and of thethermostatic. expansion valve of FIG. l, the expansion valve being shownin section.

Description of the preferred embodiment Referring first to FIG. l of`the drawings, a centrifugal refrigerant compressor C is driven by anelectric motor M. A casing extends around an upper motor compartment MC,and around a lower oil cooler compartment 11. The outlet of thecompressor C is connected by discharge gas line 12 to the inlet ofcondenser 13, the outlet of which is connected through liquid line 14and expansion valve 15 which may be any conventional expansion valve, tothe inlet of evaporator 16, the outlet of which is connected by suctiongas line 17 to the inlet of the compressor C. The liquid line 14 is alsoconnected by liquid line 19 containing a thermostatic expansion valve20, to refrigerant inlet 21 of the casing 10. The casing 10 has arefrigerant outlet 22 connected by suction gas line 23 to the suctiongas line 17. The expansion valve has a diaphragm -chamber 24 connectedby capillary tube 25 to thermal bulb 26 in heat exchange contact withthe suction line 23.

The oil lines on FIG. 1 are dashed lines. Lubricating oil is drawn fromthe compressor-motor unit through oil line 30 by pump 31, and is pumpedby the latter through oil line 32 to the oil inlet of header 34 of theoil cooler compartment 11. The oil outlet of the header 34 is connectedby oil line 35 to the compressor-motor unit.

Referring now to FIG. 2 of the drawings, the casing 1t) has a wall 38extending around the motor M, and has a wall 39 below and connectingwith the bottom of the wall 38. The bottom portion of the wall 33, thewall 39 and the header 34 extend around the oil cooler compartment 11.The bottom of the wall 39 has the refrigerant inlet 21 extendingtherethrough. The top of the wall 38 has the refrigerant outlet 22extending therethrough. The cornpartment 11 contains closely spaced,parallel oil cooler tubes 40 having return bends which are not shown, attheir left ends, their other (right) ends opening into the header 34. Apartition 36 extends horizontally across the interior of the header 34,and separates the oil inlets and outlets of the tubes 40. The usualhorizontal and vertical bales which are not shown, cause the refrigerantentering the inlet 21 to flow over the outer surfaces of the tubes 40along their entire lengths. The bottom of the wall 38 has, above `therefrigerant inlet 21, a refrigerant opening 43 connecting the motorcompartment MC with the oil cooler compartment 11. The motor compartmentMC, including the motor M, are disclosed in detail in the copendingapplication of John G. Johnson, Ser. No. 601,359, tiled Dec. 13, 1966.The bottom of the Wall 38 has a recess 45 below spaced-apart slots 46formed in the inner surface of the wall 38, and extending around themotor M on opposite sides of a central annular slot 47' in the innersurface of the wall 38, which slot connects with the refrigerant outlet22. Stator 48 of the motor M has a central passage 49 aligned with andconnecting with the annular slot 47.

The thermostatic expansion valve 20 has a partition 50 with a valveopening 51 in its center, extending across its interior. Diaphragm 52within the diaphragm chamber 24 is attached at its center to one end ofpiston rod 53 which extends through the opening 51, and has a valvepiston 54 on its other end. A circular plate 55 on the inner end ofadjusting screw 56 threaded into the end of the valve 20 opposite itsdiaphragm chamber 24. A coiled spring 57 is attached at one end to theplate 55, and at its other end to a circular plate 58 similar to andaligned with the plate 55, and aligned with the piston 54. The partitionhas a bleed port 60 extending therethrough and operating as a by-passaround the valve opening 51. The valve 20, except for the bleed port 60,is that disclosed on pp. 301-302 of Principles of Refrigeration I 3 byR. I. Dossat, published in 1961 by John Wiley & Sons. The bleed port 60is sized to provide sufficient refrigerant to cool the oil flowingthrough the oil cooler tubes 40 sufiiciently regardless of themodulation of the expansion valve caused by variations of the coolingload of the motor M.

Operation Referring rst to FIG. 1 of the drawings, discharge gas fromthe compressor C flows through the line 12 into the condenser 13. Liquidflows from the latter through the liquid line 14 and the expansion valve15 into the evaporator 16. Gas from the latter flows through the suctiongas line 17 to the suction side of the compressor C. Liquid refrigerantalso flows from the liquid line 14 through the liquid line 19 and theexpansion valve 20 into the refrigerant inlet 21 of the casing 10. Gasflows from the interior of the casing 10 through the suction gas tubes23 and 1'7 to the suction side of the compressor C. Lubricating oil isdrawn through the oil line from the compressor-motor unit by the pump31, and is forced by the latter through the oil line 32 into the header34 of the oil cooler compartment 11, and from the header 34 through theoil line 35 back to the compressor-motor unit.

Referring now to FIG. 2 of the drawings, refrigerant from the expansionvalve 20 flows through the refrigerant inlet 21 into the oil coolercompartment 11 around the outer surfaces of the oil cooler tubes 40, andthen through the opening 43 in the casing wall 38 into the recess 45within the wall 3S. The refrigerant then flows from the recess 45through the slots 46, and cools the motor M as described in thepreviously mentioned Johnson application. Gas flows through the passage49 into the annular slot 47, and from the latter through the refrigerantoutlet 22 into the suction gas tube 23. The oil entering the header 34ows through the tubes 40, then from the header 34 through the oil line35 to the compressor-motor unit.

The oil cooler load is not reduced in accordance with reductions in thecompressor load as is the motor cooling load so that the thermostat 20can be adjusted by its response to superheat in the gas leaving themotor compartment to so near closed position that the oil flowingthrough the oil cooler tubes 40 is not adequately cooled. The bleed port60 prevents this, it supplying in a by-pass around the adjustable valveopening of the valve 20, sufficient refrigerant into the oil c-oolercompartment to adequately cool the oil at all times.

By cooling the oil and the motor in a single refrigeration circuit, thetubing and tubing connections are simplied, and their cost is reduced.Adequate cooling of the oil is accomplished by placing the oil coolerupstream with respect to refrigerant flow, of the motor, and byproviding the bleed port 60. Further simplification of structure, andreduction of cost are accomplished by forming the oil cooler compartmentin the motor casing.

We claim:

1. In a refrigeration system including a compressor, a condenser, adischarge gas line connecting said compressor to said condenser,expansion means, a first liquid line connecting said condenser to saidexpansion means, an evaporator, a third line connecting said expansionmeans to said evaporator, and a first suction gas line connecting saidevaporator to said compressor; said compressor having an electricdriving motor and being connected with said motor in a compressor-motorunit; said motor having a casing with a wall extending around said motorand forming a motor compartment; said unit having an oil coolercompartment with a refrigerant inlet and a refrigerant outlet, andhaving means for circulating the lubricating oil of said unit throughsaid cooler compartment in heat exchange with refrigerant flowingbetween said inlet and outlet; the improvement comprising a secondliquid line containing a thermostatic expansion valve connected to saidfirst liquid line and to said inlet of said cooler compartment; meansconnecting said outlet of said cooler compartment to the interior ofsaid motor compartment, and a second suction gas line connected to saidinterior of said motor compartment and to said first suction gas line,said expansion valve having a refrigerant metering opening, and havingmeans including means responsive to superheat in the gas owing throughsaid second suction line for variably opening and closing said opening,said expansion valve having a bleed port bypassing said meteringopening, said bleed port being sized to supply a substantial quantity ofrefrigerant to said cooler compartment suicient to adequately cool theoil flowing therethrough when said metering opening is closed.

2. The invention claimed in claim 1 in which said cooler compartment hasa header, in which said casing has a second wall forming with a portionof said first mentioned wall and said header said cooler compartment, inwhich said inlet of said cooler compartment is an opening in said secondwall, in which said outlet of said cooler compartment and said meansconnecting said outlet of said cooler compartment to said interior Ofsaid motor compartment is an opening in said portion of said firstmentioned wall, in which said cooler compartment has a plurality oftubes therein connecting with said header, and in which said means forcirculating oil through said cooler compartment includes said tubes, andincludes an oil inlet opening and an oil outlet opening in said header.

References Cited UNITED STATES PATENTS 2,151,565 3/1939 Robinson 62-4693,146,605 9/1964 Rachf'al 62-505 3,270,521 9/1966 Rayner 62-469 MEYERPERLIN, Primary Examiner,

